Research: Oxoruthenates

Oxoruthenates

A flux technique for effective growth of large single crystals of ruthenate based materials was optmized. This technique opens the means to study such compounds in detail on electronic and magnetic properties in dependence of composition and crystallographic structure details. Target phases are alkaline-earth metal ruthenate systems with additional transition metal constituents. Previous studies revealed that it is possible to substitute particularly Ru by magnetically innocent Al or Ga within interesting substitution mechanisms. By aliovalent substitution with transition metals the concentration of mobile charge carriers is proposed to be controlled in respective spin-ladder compounds. Another family of layered ruthenates that may give rise to interesting physical properties with technological potential is Ru-based ferrites with Mn, Fe, and/or Co. These materials are soft ferromagnets with low coercive fields and very high Curie temperatures. The electronic structures and physical properties can be tuned by simple chemical substitution and thus by varying the relative concentration of 3d and 4d elements. The promising combination of properties provide a fertile ground for fundamental studies and open up a host of potential device applications particularly in the developing field of spintronics.

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Large single crystals of ruthenates with further 3d metals are obtained from chloride-melts. The diagram shows for the example of Sr(Ru,Fe)6O11 the dependence of the band gap and the Curie temperature from the composition.